The present invention relates to a lubricating oil composition and a concentrate therefor which provides low sulfated ash while meeting high performance standards.
There is continuous need for improving the performance characteristics of automotive gasoline and diesel engines and the lubricating oils used therein. For example, modern diesel engines are sometimes fitted with a particulate trap to minimize the amount of particulates which are emitted to the atmosphere as pollution. Such particulates may include soot from incomplete combustion but also include ash of various types, much of which is non-volatile metal compounds originating from metal-containing additives in the fuel or, especially, in the lubricant. Excessive ash buildup in particulate traps is a concern because certain types of metal-containing ash are not readily removed from the trap, thus making the regeneration and reuse of such traps difficult if not impossible.
Despite these drawbacks from the use of metal compounds in lubricants, additives, including metal-containing additives, have been used for many years and will likely continue to be used for many years in the future. This is because metal-containing additives perform essential functions in motor oils and other lubricants. Certain metal salts are detergents, which serve to neutralize acidic combustion products which make their way into motor oil. Others are dispersants or antiwear agents. To simply reduce or eliminate the amount of metal-containing additives from a motor oil would lead to failure of the oil in many industry-mandated performance tests.
There are industrial performance criteria which must be met for a variety of lubricant applications. Among the most important are those for diesel engines and those for gasoline engines. A useful lubricating oil will be able to pass the tests for both types of engines. Thus a reduced-ash lubricant which would pass the diesel engine performance tests but would fail gasoline engine tests would have only limited usefulness and would not be commercially acceptable as a universal engine lubricant.
There has been a great deal of research reported on various lubricant formulations to solve specific problems. For example, U.S. Pat. No. 4,938,881, Ripple et al., July 3, 1990, discloses lubricating oil compositions and concentrates which comprise a lubricating oil, the product of reacting a substituted succinic acylating agent with an amine, a basic alkali metal salt of sulfonic or carboxylic acid, a metal salt of a dihydrocarbyl dithiophosphoric acid, and optionally a neutral or basic alkaline earth metal salt of an acid organic compound.
U.S. Pat. No. 3,853,774, Crocker, Dec. 10, 1974, discloses oil-soluble basic magnesium salts. They may be used in oil formulations which contain alkenyl succinimide, carbonated sulfurized calcium polypropylene phenate, and zinc dithiophosphate.
U.S. Pat. No. 3,384,587, Holst et al., May 21, 1968, discloses a hyperbasic calcium sulfonate lubricating oil composition which also includes dispersants such as oxylated nonyl phenols of the formula C.sub.9 H.sub.19 --Ar--(OCH.sub.2 CH.sub.2).sub.n OH [Ar is a benzene ring] where n is an average integer of from 2 to 9.
U.S. Pat. No. 2,647,873, Matthews et al., Aug. 4, 1953, discloses a lubricating composition including a class of compounds which are suitable as additional agents. An example given is the product of para-octyl phenol, calcium hydroxide, and formaldehyde.
There has now been found a lubricating oil composition which is significantly reduced in ash-forming additives but which still meets demanding performance requirements for both gasoline and diesel engines.